This invention relates to a city water flushing and sludge prevention control system for use in a city water system having a plurality of street water mains interconnected by branch water mains and having hydrants connected to the branch water mains.
Maintaining and monitoring water quality is becoming increasingly important to most water utilities. In the United States, for example, the Safe Drinking Water Act amendments of 1986 have caused many water utilities to pay very close attention to the quality of water they are providing to their customers. Also, these new regulations require more sampling of the water from points out in the distribution system. These samples are taken on a regular basis and then tested.
U.S. Pat. No. 5,201,338 (herein incorporated by reference) discloses a system and device for flushing water mains and for taking samples from hydrants attached to the water mains. Although the '338 patent can be used to flush water mains using the novel flushing hydrant described therein and to take water samples, there remains a very serious problem in flushing water mains using the flushing hydrant of the '338 patent, other flushing hydrants, or fire hydrants.
The problem is best described by reference to FIG. 1, which shows the usual layout of a city water system.
In a city water system, street water mains M generally run down city streets and have a number of branch water mains B which interconnect the street water mains M. In turn, buildings are connected to the branch water mains B. The branch water mains B also have fire hydrants H attached at various points.
It is known that sludge may accumulate in the branch water mains B unless they are periodically flushed. Flushing is typically done by opening hydrant H.sub.1 attached to a branch water main B. However, because of the path of least resistance, water will generally only flow from the street water main M.sub.1 closest to the branch water main B with the open hydrant H.sub.1, and not from the street water main M.sub.2 more distant from the branch water main B with the open hydrant H.sub.1. Therefore, the segment B.sub.1 of the branch water main B between street water main M.sub.1 and the hydrant H will be flushed, but the segment B.sub.2 between hydrant H.sub.1 and street water main M.sub.2 will not be flushed. Also, the attachment pipes between buildings and segment B.sub.2 will not be flushed.
Applicant has found that the buildup of sludge in the unflushed segments of the branch water mains B and the attached buildings can cause damage to copper pipes in the buildings if the sludge contains erosive materials.
There is a need for a sludge prevention control system that allows the segments B.sub.2 between the flushing hydrant H.sub.1 and the more distant street water main M.sub.2 to be completely flushed. There is also a need for a sampling apparatus that allows sludge to be detected and analyzed for erosive materials while the mains are being flushed.